I do not know why you are having sudden anxiety and I hope you find a relief but I wonder few things that you can consider in your own time and space.
What exactly was happening before you felt the anxiety?
What do you do about it in the past?
Where in your body do you feel it hits?
Are there others whom you really value their relationship to you but ....there is history or unresolved issues and you are not ready to explore that today?
Just asking these questions and hope as you ponder you listen to the body and see if the answers resonate with you and release the tension or make you grip to the anxiety more.
PS. I will also caution you not to self-diagnose yourself. These can be trap for all of us. You may or may not have PTSD or something else but at the end of the day, you want to be here and now and be your own in your body...so hope you keep an open mind.